Cathode construction for thermionic devices



Jan. 31, 1928. 1,657,986

V.K.ZWDRYNN CATHODE CONSTRUCTION FOR THERMIONIC DEVICES Filed July 19. 1921 0 .12 f 1 o J H a 5/ k4 In J L wnuzsszs; INVENTOR Patented Jan. 31, 1928.

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VAN'IA.

Application filed July 19,

My invention relates to evacuated electric devices and particularly to a novel cathode structure which may be employed in such devices.

@ne object of my invention is to provide a cathode structure which is of unusual rigidity and strength of construction and which admits of the elimination of the adjusting springs heretofore employed to compensate for the expansion and contraction of the filament.

Another object of my invention is to provide a low-voltage, high-current filament wherein the effects of the magnetic fields set up by the filament currents upon the elec tron emission therefrom may be neutralized to a large'entent.

Still another object of my invention is to provide such a filament-supply system that the effects of the potential drop along the filament upon the electron emission therefrom may be reduced to a low value, thereby providing a filamenthaving the characteristics of an equipotential cathode.

A. further object of my invention is to provide a filament structure especially adapted to externally controlled tubes which tends to protect the walls of the tube immediatel adjacent the filament from such elec tron ombardment and heat radiation as emanates from the filament.

Other objects of my invention will appear from the followingdescription when taken a in connection with the accompanying drawings and claims:

Heretofore, the normal operation of electron tubes has been adversely affected by the potential drop along the filament and by the magnetic field surrounding the filament, resulting from the passage ofthe exciting currents therethrough. Furthermore, in the manufacture of vacuum tubes, considerable difficulty has been experienced in so adjusting the filament as to maintain the tension thereof constant during the periods ation and nonoperation.

Additional difficulties have been eizpen ienced in the operation of vacuum tubes, especially externally controlled tubes, in that the surface of the tube opposite the hot cathode tends to be destroyed by reason of the electron bombardment and heat radiation emanating from the filament, as just mentioned. i

of oper- GATIEIOIDE CUNSTRUCTION F013, THERMIGN 1E0 DEVICES.

1921. aerial No. 485,94t9.

7 According to my invention, 1 provide a filament structure wherein expansion of the heated element may take place without serious distortion thereof; wherein the efiects of the potential drop and of the magnetic fields, resulting from the passage of the filament currents, are reduced toa minimum value; and wherein the'surface of the walls of the tube opposite the filament is protected.

Briefly speaking, the filament structure embodying my invention comprises a filament, which is supported upon one face of an i sulating supporting member having op- One of the supply conductors is connected to the filamentat spaced points and the other supply conductor is connected to the filament at spaced points intermediate the first-named points to divide the filament into a number of parallel sections, wherein the current flow in each section is opposite to the current-flow in the sections immediately adjacent.

A better understanding of my invention may be had by referring to the accompanyinp; drawings, wherein Fig.1 is a diagrammatic view of the fila ment and supply circuits therefor embodyinn; my invention;

Fig. 2 is a front elevational view of the insulating supporting member upon which the filaments and conductors of Fig. 1 are mounted;

Figs. 3 and t are rear elevational views and front elevational views, respectively, of

faces for supporting the filament 2 and the supply conductors 8 and 4. lhe supply conductors 3 and a, which are disposed adjaill member 13 which is mounted in a press Bill cent one face of the insulating strip 5, are alternately connected to the filament 2, which is disposed adjacent the opposite face of the insulating strip, at spaced points 6 by conductors 'i' which extend through staggerec holes 8 in the supporting aember 5.

l fhilethe filament 2 has been shown as supported by the conductors T, which or;- tend through the holes 8 to connect the sup ply conductors 8 and l to the filament 2, it is apparent that the filament 2 may be also supported at spaced points by projections (not shown) which extend from the supporting member 5 or. by being cemented to the supporting member 5.

It will be noted that, in such an arrangement,'the filament 2 is divided into a plurality of parallel-connected sections 9, the current-flow in each section being opposite to the current-flow in the sections immediately adjacent thereto, as indicated by the arrows in Fig. 1.

In Fig. 5 is shown an evacuated electric device 11, of the Fleming; type, employing; a cathode construction. just described. though I do not wish to be limited to such arrangement of electrodes. llhe evacuated electric device, just mentioned, comprises the cathode structure 1 and an anode 12. The anode 12 is supported by a conductingle The cathode structure 1 is supported by means of the conductors 15 and 16 which are also mounted in the press 14- The cathode structure 1 and the anode 12 are preferably disposed in parallel planes, the hot cathode 2 facing the anode 12, as shown.

. One advantage of my invention is the pro- .vision of a cathode structure which is simple in design and rugged in construction.

Another advantage of my invention is the provision of a cathode structure which is especially well adapted to alternating-current'filament excitation by reason olf the relatively large currents which are permitted to traverse the filament sections, all as will be understood by those skilled in the art.

Still another advantage of my invention is the provision of a filament of irregular outline which is supported at a plurality of spaced points, thereby providing a filament structure which admits of expansion and contraction of the filament without undue distortion thereof. Other advantages of my invention will be apparent from the foregoinn description.

While I have shown a particular type of construction for the filament structure embodying' my invent-ion, it is capable of various changes and modifications without departing from the spirit ot' my invention. "l desire. therefore. that only such limitations shall be imposed thereon as are indicated in the appended claims.

menses ll claim as my invention:

1. A cathode structure comprising a heated filament, a plurality of supply conductors connected to load currents into said lilament at spaced points and a plurality ct supply conductors conrected to lead currents from said iilameut at points intermediatc said first-named points.

2. it cathode structure comprising a heated filament of irregular outline, means for supportinc; said lilaincut, a plurality of sup ply conductors connected to lead currents into said filament at spaced points and a plurality of supply crnductors connected to lead curre s lilamcnt at points interniediate named points.

3. A filament structure comprisiiula heal ed element, means for supporting: J element, a supply lead connected to said. element at spaced points. and a second supply lead connected to said element points intermediate said first-named points.

l. A. filament structure comprisine a plu- 'aliry oi filament sections connected in parallel. each section be ng); oppositely connected. W 'cal sense with respect to the tilaiu sec; s immediat y adiacc t rod ir'ieans tor energizing; said filament sections.

5- A filament structure comprising; a pluo'l filament sections, forming)- one lilaa snpport iur member. and conductor siipp cmc'mliucf troi'n said supporting men'iber to the junction ot said sections tor sup 'iort rur said iihnnent sect ons and 'lor conne ting said filament sections in para lel relation with currents flowing; in opposite directions in adjacent sections.

6. A 'lilfunent structu e compr sing a plurality oi filament sections of Zia-nag; outline, a supporting; member, and conductors supported by said supporting member for supportino' said filament sections and for conneet-i said li an'ient sections in parallel, each "filament section being; oppositely connected with respect to the filament sections immediately adjacent thereto.

7. A filament structure comprising; a plurality oi? filament sections, united into a filament, an insulating; supporting" member, and conductor supports extending trom said supporting member to the junctions ot said sections tor supporting; said filament sections and for connectingsaid filament sections in parallel relation.

8. A filament structure comprising; a plurality ct filament sections arranged in series relation. an insulating support therefor havinp; opposite faces and incon'iinc and out connections, whereby each filament section may be traversed by currents opposite to those in the filament sections immeuiately adjacent thereto said connections being; mounted on and supported by said insulating support and securing the filament sect-ions thereto.

and a second supply lead connected to 20 heated element, a

9. A filament structure comprising a heated element, an insulating support therefor having opposite faces, a supply lead connected to said filament at spaced points said filament at spaced points intermediate said first-named points.

10. A filament structure comprising a heated element, an insulating support therefor havingopposite faces, said opposite faces being substantially parallel, a supply lead connected to said filament at spaced points and a second supply lead connected to said filament at points intermediate said first named points, said heated element being supported upon one of said parallel tacos and said supply leads being disposed immediately adjacent said opposite parallel face.

11. A filament structure comprising supply lead connected to said filament at spaced points, asecond supply lead connected to said filament at points intermediate said first-named spaced points, and an insulating member tor supporting said heated filament and said supply leads and for insulating said heated element and said circuit conductors.

12. In a vacuum tube device, a combined cathode structure, including a filament support of insulating material having two opposite faces, a pair of conductors extending along one of said faces, a filament extending along the other face oi said insulating support and means for securing said filament,

insulating support and pair of conductors together, and supporting conductors at tached to said pair of conductors, whereby said supporting conductors hold the combined cathode structure.

13. In a cathode structure, a filament support of insulating material, a pair of parallel conductors extending along one face of saidsupport, said support having two rows of holes, one row along each of said conductors, the holes in said rows beingstaggered, a filament upon the opposite side of said support and filament connections extending through said holes and uniting said filament and said conductors.

14:. In a cathode structure, a filament support of insulating material, a pair of parallel conductors extending along one face of said support, said support having two rows of holes, one row along each of said conductors, the holes in said rows being staggered, a filament extending in zig Zag form along one side of said support between said rows of holes, the filament extending from one row to the other, and conducting attaching means extending through said holes and connecting said filament with said parallel conductors.

15. In a vacuum tube device, a filament, a supporting body of insulating material to which said filament is attached and a pair of supporting conductors extending through the wall of the vacuum tube and holding said supporting body spaced away from said wall.

In testimony whereof, I have hereunto subscribed my name this first day of July, 1921.

VLADIMIR K. ZWORYKIN. 

